The invention pertains to the field of apparatus for injection of a fluid for an exhaust gases treatment device of an internal combustion engine arrangement.
It is known to install a Diesel Particulate Filter, or “DPF”, on an exhaust line of a Diesel engine in order to temporarily store soot and non-burnt particles present in the exhaust gases of such an engine. Such a DPF must be regularly cleaned by oxidation of the particulate materials. In order to obtain such an oxidation, the temperature of the exhaust gases must be substantially increased. This can be achieved thanks to a burner installed in the exhaust line of the engine next to the DPF. This can also be achieved thanks to an oxidation catalyst installed in the exhaust line, upstream of the DPF. In both cases, fuel is injected in the exhaust line, either to be burnt by the burner or to come into contact with the catalyst. In both cases, the temperature of the exhaust gases increases when they enter the DPF, which enables full oxidation of the particulate materials in the DPF.
It is also known to equip diesel engine arrangements with a device for removing nitrogen oxides from the exhaust gases using selective catalytic reduction, which involves injection of a nitrogen containing fluid, such as a urea-water solution, in the exhaust gases upstream of a dedicated catalytic converter.
Therefore, many engine arrangements are equipped with an apparatus for injection of a fluid for an exhaust gases treatment device. In many cases, such an apparatus includes a fluid injector which is fed from a source of fluid under pressure through a fluid conduit, and which is adapted to inject fluid in the flow of exhaust gases within an exhaust line of said engine arrangement and upstream of said treatment device. In many cases, the injector is electromagnetically controlled. It is known to provide a feed valve in the fluid conduit between said source of fluid and said injector for controlling the delivery of fluid.
One key aspect of these fluid injection systems is that they operate usually only intermittently, only under certain engine operating conditions. The rest of the time, no fluid is injected by the system. During those times where the system is inoperative, the fluid contained in the system may be subject to degradation. For example, the injector is close to the exhaust line and is therefore subject to quite high temperatures. In case of a system for injecting fuel, the fuel trapped in the injector may be subject to coking, which brings the deposit of carbon substances inside the injector, which may cause the injector to become jammed. Therefore, it is known to equip such an injection apparatus with a purge system for purging the fluid conduit, said purge system comprising a gas conduit connecting a source of pressurized gas to the fuel conduit so that the gas pressure can be used to purge at least part of the conduit. According to a known system, the purge system is equipped with its own electromagnetically controlled valve for controlling the purge operation.
Of course, this additional purge valve is a source of cost, especially if it is taken into account the control unit which is needed for its control. Such a purge system is also rather cumbersome, which is more and more a problem when it comes to integrating the system on a vehicle where space is more and more limited.
Therefore, there is a need to provide an injection apparatus with a purge system that is both cheap and effective, and less cumbersome that the existing designs.
According to an aspect of the present invention, an apparatus is provided for injection of a fluid for an exhaust gases treatment device of an internal combustion engine arrangement, said apparatus including:
an electromagnetically controlled fluid injector fed from a source of fluid under pressure through a fluid, conduit, and adapted to inject fluid in a flow of exhaust gases within an exhaust line of said engine arrangement;
a feed valve in the fluid conduit between said source of fluid and said injector for controlling the delivery of fluid;
a purge system for purging the injector, said purge system comprising a gas conduit connecting a source of pressurized gas to the fluid conduit;
characterized in that the purge system further comprises:                a pressure limiter within said gas conduit; and        a check valve downstream of said pressure limiter for preventing backflow from the fluid conduit towards the gas source, and in that        the pressure limited by said pressure limiter is lower than the pressure of fluid delivered by the source of fluid in the fluid conduit downstream of the feed valve.        